The present invention relates to a device for the controlled “osseodisintegration” of partially or completely osseointegrated implants by forming a denatured tissue layer in the implant bedding where the layer is preferably very thin. The denatured layer then allows the atraumatic removal of the implant which conserves as much of the bone material surrounding the implant as possible.
It is known that medical implants can be used for therapeutic purposes. Some types of implants are designed to adhere to the bone of the subject. If such a connection is formed it is also termed osseointegration. Osseointegration generally refers to the structural and functional connection between living bone and the surface of a load-bearing implant. Preferably said connection is direct such that no scar tissue, cartilage or ligament fibers are present between the bone and the implant surface. An osseointegrated implant is mostly a type of implant which comprises pores into which osteoblasts and supporting connective tissue can migrate to form said connection. When osseointegration occurs, the implant is tightly held in place by the bone. The process typically takes several weeks or months to occur.
In dentistry, implants capable of osseointegration are used as so-called dental implants onto which (aesthetic) prostheses are attached, to replace one or more missing teeth. A dental implant showing typical implant elements is disclosed in e.g. EP 2 412 335 A1. In other medical fields implants capable of osseointegration are used mostly when the implant is load-bearing such as when implanting total joint replacement prostheses. If the implant is not intended for osseointegration, the implant will typically be cemented into the subject by using a suitable cement composition. Examples are cemented and/or cementless endo-prostheses as total joint replacement for hip, knee, shoulder, elbow, and spine.
Implants in medicine are shaped very differently depending on the use. These implants are frequently made of inorganic material such as a specific metal, a metal alloy or a ceramic. In dentistry, the dental implants which are most frequently used have a mostly helical shape which can be screwed into bone and typically are made of titanium, titanium alloys or sometimes ceramics. Exemplary schematics of dental implants (A) are shown in FIG. 1A and FIG. 2 of this application.
The surfaces of the implants can be conditioned (e.g. roughened) by various methods to achieve a good growth of the bone tissue onto the enlarged contact surface. It is critical that the implant is successfully osseointegrated. During the time of healing it can occur that the implant is only partially osseointegrated. Also implants which have been implanted in the patient for some time may lose part or all of the osseointegration. This process is also referred to as osseodisintegration. In these cases it seems sensible to speak of “unwanted” osseodisintegration whereas this invention refers to intentionally induced, “intended” osseodisintegration. If an implant completely loses osseointegration this usually results in a loosening of the implant relative to the bone so that the implant can be removed generally without much trauma to or destruction of the bone material. For example, screw implants can be removed by unscrewing the implant. Sometimes, especially in orthopedics, a new implant can be set in the same surgical procedure or mostly after the old implant was removed and the bone tissue had sufficient time to heal.
Often, however, it becomes necessary to remove an implant which is still partially or fully osseointegrated. This situation can arise for example if an implant failed to be completely osseointegrated after implantation or when an implant is in an incorrect position or when an irreparable fracture occurred in the implant or when there is an active inflammation in the implant bedding (periimplantitis).
In such cases, the current treatment procedure is that the implant is removed by drilling out, cutting out or milling off sufficient bone surrounding the implant such that the implant is freed from the bone material and can be removed. The harm done to the bone material in such a procedure is quite severe resulting in a large loss of bone substance. The gap made between the bone and the implant is typically at minimum 2 mm to make it possible that sufficient cooling agent can be flushed into the gap. Furthermore, such gap is also a result of drilling, cutting and milling equipment which must be structurally sufficiently stable and hence sufficiently thick to remove the bone material.
If a dental implant having mostly a diameter of only about 3-6 mm is removed in this way, this treatment may result in a bone cavity which is almost twice the diameter of the cavity in which the implant was originally located. As a consequence of the large loss of bone substance, it becomes frequently difficult to insert a new implant. If sensitive anatomical structures are close by, which is very often the case, the removal of the implant by this traditional method bears a very high risk of permanently damaging these structures. To avoid these risks sometimes the compromised implant will be left in place, sometimes even without using it, as so called “sleeping implant”.
An alternative treatment has been described to “unscrew” a partially or fully osseointegrated implant by using strong forces, breaking the bone structure. Of course such large forces required to remove the implant result in a very uncomfortable situation for the patient during the removal of the implant and also include a high risk of permanently damaging sensitive anatomical structures.
Thus, there is still a high and unmet need for a safe and effective means for removing partially or completely osseointegrated implants from bone without destroying a large part of the bone material in the process. Also implants are needed which can be easily removed from bone material once there is the indication for removing the implant.